察尔汗盐湖区线形沙丘下伏湖相地层的释光年代及其环境意义

本研究尝试使用钾长石多步升温红外后红外法 （MET-pIRIR） 对察尔汗盐湖北侧线形沙丘下伏古湖相沉积物进行年代测定，并初步探讨其古环境意义。结果表明：钾长石MET-pIRIR₂₅₀法能够得到等效剂量坪区，说明长石信号能够充分晒退并且异常衰减对测年结果的影响可以忽略，从而保证了测年结果的可靠性；古湖相沉积顶部200—180 ka的年代证实了深海氧同位素7阶段柴达木盆地大规模湖泊的存在；上覆地层缺失表明即便在柴达木盆地沉积中心附近，地表沉积物的侵蚀（主要为风蚀）也十分严重，以至于在冰期尺度上也难保证连续性；这一年代结果也表明湖泊的演化并非造成线性沙丘较年轻（3—0 ka）的直接原因。钾长石MET-pIRIR法的应用对解决盆地内中、晚更新世古环境、古气候、地貌演化等问题具有重要意义。

Luminescence chronology and environmental implications of palaeolacustrine sediments beneath linear dunes in northern Qarhan Salt Lake region

Studies of late Quaternary geomorphic evolution and paleoenvironmental changes in the Qaidam Basin had been hindered by chronology.In this study,multiple-elevated-temperature post-IR IRSL(MET-pIRIR)procedure of potassium feldspar was applied to date surficial paleolacustrine sediments beneath linear dunes in northern Qarhan Salt Lake region,close to the depocenter of the Qaidam Basin,based on which the palaeoenvironmental implications were discussed preliminarily.The results showed that:An obvious De plateau between the stimulation temperatures of 250℃and 290℃indicated the anomalous of the IRSL signals of K-feldspar were negligible,thus ensuring the reliability of the dating results;The ages,ca.200-180 ka,of paleolacustrine sediments supported the existence of a mega Qaidam Lake during Marine Isotope Stage 7;The absence of overlying sediments indicated severe wind erosion in surficial sediments in the depocenter of the Qaidam Basin,reminding that the sedimentary records were difficult to keep continuous even in glacial-interglacial scale;The huge hiatus between late Holocene linear dunes and mid-Pleistocene lacustrine sediments implies that the late accumulation of linear dunes was not directly hindered by the existence of the mega Qaidam Lake.The application of potassium feldspar MET-pIRIRdating will be crucial for the studies of paleoenvironmental,paleoclimatic,and geomorphologic evolution in the Qaidam Basin since mid-Pleistocene.